The Journal of Chemical Physics· 2026Q1
The std2 package: A computationally efficient program to calculate molecular response properties and excited states using simplified quantum chemistry methods
- 1citations
- Q1SCImago
- 2026year
Short summary
The std2 program package introduces simplified quantum chemistry methods (sTDA, sTD-DFT, XsTD-DFT, etc.) enabling routine excited-state and molecular response property calculations on systems with thousands of atoms, achieving 2-3 orders of magnitude speedup over standard TD-DFT.
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Key points
- The std2 package implements simplified quantum chemistry methods (sTDA, sTD-DFT, XsTD-DFT, etc.) for excited states and molecular response properties.
- XsTD-DFT shows improved description of charge-transfer excitations compared to sTD-DFT.
- Calculations achieve 2-3 orders of magnitude speedup over standard TD-DFT.
- The package supports routine calculations on systems with thousands of atoms, including explicit solvent effects (AQM).
AI-generated from the title and abstract; the full text is not read.
Abstract
The std2 modular program package is dedicated to the computation of excited states and molecular response properties using simplified quantum chemistry approaches. The framework involves several variants of the simplified time-dependent density functional theory, including sTDA, sTD-DFT, SF-sTD-DFT, XsTDA, XsTD-DFT, and SF-XsTD-DFT methods. Combining controlled approximations with efficient implementations, the std2 program enables routine calculations on systems containing thousands of atoms while retaining a favorable balance between computational cost and predictive accuracy. Therefore, the framework supports all-atom quantum mechanics (AQM) methodologies for the treatment of surrounding and dynamical structural effects considering realistic systems. In this contribution, the capabilities of the std2 package are illustrated for spectroscopic observables, such as one- and two-photon absorption, electronic circular dichroism, optical rotation, second-harmonic generation, and excited-state absorption. Among results, benchmark calculations show that the recent XsTD-DFT scheme improves the description of excited states relative to sTD-DFT especially, for charge-transfer excitations while preserving a speedup of two to three orders of magnitude compared to standard TD-DFT. Applications of AQM methodologies to explicitly solvated systems and ultra-large systems are also highlighted, showing the adequacy of the std2 program to treat such systems. Overall, std2 provides an efficient platform for large-scale excited-state and spectroscopic simulations, especially in AQM protocols.
The authors' abstract, as published at the source. The Journal of Chemical Physics, 2026 · DOI ↗
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Field: Atomic and Molecular Physics, and Optics
Atomic and Molecular Physics, and OpticsPhysics and Astronomy